This section provides background information to facilitate a better understanding of the various aspects of the disclosure. It should be understood that the statements in this section of this document are to be read in this light, and not as admissions of prior art.
A rotorcraft or rotary-wing aircraft is a heavier-than-air flying machine that uses lift generated by rotor blades that revolve around a mast. Several rotor blades mounted on a single mast via a yoke or yokes is referred to as a rotor hub. A standpipe assembly attached to a gearbox and attached to the mast via a slip ring is used to channel wiring through the gearbox and the mast of the rotorcraft. The slip ring includes a rotor attached to the mast and a stator attached to the standpipe assembly. The slip ring transmits electrical power between the non-rotating components and the rotating components of the rotor hub. The standpipe assembly is subject to angular and axial displacement due to mast bending during operation of the rotorcraft. Standpipe assemblies typically incorporate a rigid coupling to connect the standpipe assembly to the slip ring.
During operation of the rotorcraft, thrust and moments of the rotor hub as well as thermal growth/shrinkage variations may cause the mast to deflect or bend. In rotorcraft applications where the slip ring is positioned above the yoke or yokes and not size constrained by the mast, the slip ring is robust enough to react the mast deflections. In recent rotorcraft applications where the slip ring is positioned within the mast and constrained by the size of the mast, mast deflections can induce high loads into the slip ring as the slip ring rotor wants to bend with the mast while the slip ring stator wants to remain stiff with the standpipe assembly. The bending movement of the rotor relative to the stator causes one to rub the other which may lead to chips and shavings of the slip ring breaking off and falling into the gearbox thus shortening the life of the slip ring and damaging the gearbox. The bending moment may also produce excessive reactive radial loads in the slip ring bearings which can lead to premature failure of the bearings.